How much does 20km of optic fibre weigh? Why don't these fibre strands suffer from the same physical limits as cabling used in suspension bridges? To be clear: I am not doubting that multi-kilometer optic fibre controlled drones do not exist. There are plenty of highly quality news sources and YouTube videos about them.
https://www.wildberries.ru/catalog/423372174/detail.aspx
Weight: 2.2 kg Price: 78 000 ₽ ($1000)
Just to clarify, this 20km fibre spool is installed on the drone itself and unwinds automatically as drone flies.